1. Field of the Invention
The present invention relates to a low-dimensional plasmon-light emitter, which can produce low-dimensional plasmon-light with an arbitrary energy over a broad range from a far-infrared region to an ultraviolet region.
2. Description of Related Art
When carriers are recombined at p·n junctions of a semiconductor or relaxed from an excited state to a ground state, luminescence is emitted. The luminescence is used in various fields, e.g. sensors, light emitters and display devices. Since an energy level of a substance is substantially determined in correspondence with its composition and structure, a luminescent energy is nearly constant in relation with the type of substance. According to prior art references, luminescent energy is varied by selection of a substance or combination of substances. That is, production of luminescence with an arbitrary energy is theoretically impossible, unless the type of substance or combination of substances is changed.
Furthermore, surface-plasmon is excited by resonating a charge density wave, which exists on a metallic surface, with light. Surface-plasmon has been applied to various sensors for detecting or measuring refractive index or absorptance of liquids, mono-molecular films, solid surfaces and so on. Application of the surface-plasmon luminescence to laser diodes is disclosed in WO 94/13044A.
Surface-plasmon luminescence is limited to light emission with an energy near a frequency of the surface-plasmon (calculated as a square root of a bulk-plasma frequency). Change of a luminescent energy necessitates selection and ultra-micronization of a material. However, the luminescent energy is mostly limited to an ultraviolet region with poor mono-chromaticity, even when the material is properly selected or prepared as fine particles.
On the other hand, low-dimensional plasmon originating in a fluctuation of a charge of density wave has the feature that its energy can be varied over a broad range in correspondence with its frequency. Such low-dimensional plasmon localizes in a two-dimensional or a one-dimensional structure. In this sense, production of luminescence with an arbitrary energy over a broad range from a far-infrared region to an ultraviolet region is estimated by changing a nanostructure in the same material without the necessity of a selection or combination of substances corresponding to an objective luminescent energy.